MinHeap

This is the program to extract the minimum element from a min heap and restore the heap property among the remaining elements...

 
/**
 *
 * @author Akshay Ratan(ARC)
 */
import java.io.*;
public class MinHeap {
    static int smallest;
    static int n;
   // static int arr2[]=new int[444];
    //static int j=0;
        public static void main(String args[])throws IOException
    {
           
    BufferedReader obj=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter the number of elements ..press enter and then enter number of elements");
                int arr[]=new int[444];
        n=Integer.parseInt(obj.readLine());
        for(int i=1;i<=n;i++){   
            arr[i]=Integer.parseInt(obj.readLine());
        }
                BuildHeap(arr);
                for(int k=1;k<=n;k++)
                    System.out.print(arr[k]+" ");
                System.out.println("Minimum element in the heap is"+" "+arr[1]);
                System.out.println("see the new min-heap!!");
                /*String y=obj.readLine();
                if(y=="Y"||y=="y"){*/
                    HeapMinExtract(arr);
                    BuildHeap(arr);
                for(int k=1;k<=n;k++)
                    System.out.print(arr[k]+" ");
               
        }

    public static void MinHeapify(int arr[],int i)
    {
        int l=2*i;
        int r=(2*i)+1;
        if(l<=n && arr[l]<arr[i])
            smallest=l;
   
        else smallest=i;
       
       
        if(r<=n && arr[r]<arr[smallest])
        {
            smallest=r;
        }
        int t;
        if(smallest!=i)
        {
            t=arr[i];
            arr[i]=arr[smallest];
            arr[smallest]=t;
        }
        }
   
    static void BuildHeap(int arr[])
    {
        double f=Math.floor(n/2);
        for(int i=(int)f;i>=1;i--)
        {
            MinHeapify(arr,i);
        }
    }
    static void HeapMinExtract(int arr[])
    {
        if(n<1)
            System.out.println("Heap underflow !!");
        else{
        int min;
        min=arr[1];
        arr[1]=arr[n]; //exchange
        n--;
        MinHeapify(arr,1);
        }
    }
       
    }